ROS are usually reduced numerous times such that you get no superoxide formation. However, if you don't have the electrons necessary to do so, you may get an accumulation of superoxide (free radical - O2-*)

Where do ROS come from?

Endogenous sources: macrophages create, NO, neutrophils

Exogenous Sources: radiation, drugs/toxins, pollutants

Ischemia Reperfusion Injury

If you have an ischemia, the has been damaged and hasn't been doing it's normal functions; therefore it doesn't have the e- necessary to reduce the ROS. (you get incomplete O2 reduction)

If you unblock the ROS, you get a buildup of ROS that the cell can't handle, and you cause more cell injury

When will you see necrosis?

Grossly: 18-24 hours

LM: 4-12 hours

after injury

What color does necrosis typically stain?

Necrosis is typically more eosinophilic (less nuclei)

Pyknosis

Nuclear shrinkage

Karyorrhexis

Nuclear Fragmentation

Karyolysis

Nuclear Dissolution

Coagulative Necrosis

Still see structure, but no nuclei

Caused by Ischemia

Eosinophilia is a typical feature

Liquefactive Necrosis

Seen in two distinct conditions:

1) Ischemia in the brain (stroke)

autolysis is dominant

2) Abscess formation just about anywhere in the body

PMNs everywhere

Gangrene

Dry - a form of coagulative

Wet - bacterial infection on top of necrosis

Gas - results from puncture wound infection

Caseous Necrosis

Cheeeeeese

Can only use this to describe it grossly.

otherwise, we're looking at a granuloma

Fat Necrosis

Two Types:

1) Enzymatic: in pancreas after acute inflammation. leakage of pancreatic ducts causes digestive enzymes to attack local fat cells. You see "ghost cells" that are more basophilic.